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Fax is not working on H323

Hello All,

I have an issue with fax, it is connected to an fxs port on my h323 gateway. When a call comes from PRI and get connected to fax after I hear the fax tone the fax drops. IOS is Version 15.0(1)M4, and DSP is PVDM3.

My analysis:

The external calls hit gateway and it matches the pots dialpeer where my fax connected to. From the "debug voip vtsp all", I see Primary Fax Protocol=CISCO_FAX_RELAY, which is not enabled and we are using T38 relay and modem passthrough method for faxing. I believe PVDM3 does not work with Cisco Relay and couldn't allocate any dsp resources for the call and it drops. But still I wonder how gateway takes cisco relay.

Config:

voice service voip

allow-connections h323 to h323

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback none

h323

  emptycapability

modem passthrough nse codec g711ulaw

!

dial-peer voice 1001 pots

tone ringback alert-no-PI

description PSTN Incoming, Pattern:.

translation-profile incoming PSTN-to-PhoneDN

incoming called-number .

direct-inward-dial

!

dial-peer voice 999030 pots

tone ringback alert-no-PI

destination-pattern 3027898

progress_ind setup enable 3

port 0/3/0

Output of vtsp debug

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

Oct  4 20:30:07: //6824/97F0D7BD8350/VTSP:(0/1/0:15):7:1:1/vtsp_dsm_save_fax_config: 

   Fax Relay=ENABLED

   Primary Fax Protocol=CISCO_FAX_RELAY, Fallback Fax Protocol=NONE_FAX_RELAY

   Fax Relay CM Suppression :=ENABLED, Fax Relay ANS Suppression :=DISABLED

   Fax Parameters Set By=Dialpeer, Peer=999030 (this is the peer where my fax connected to)

I have converted the port to MGCP and found its working, while faxing I see vtsp outputs

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

Oct  4 23:57:29: //7181/8FE17FEF8379/VTSP:(0/3/0):-1:1:2/vtsp_dsm_save_fax_config:

   Fax Relay=DISABLED - MGCP Application

   Primary Fax Protocol=IGNORE_FAX_RELAY, Fallback Fax Protocol=IGNORE_FAX_RELAY

   Fax Relay CM Suppression :=ENABLED, Fax Relay ANS Suppression :=DISABLED

   Fax Parameters Set By=MGCP Call Type --> I believe MGCP disabled the cisco fax relay and switch over to T38.

Oct  4 23:57:40: //7181/8FE17FEF8379/VTSP:(0/3/0):-1:1:2/vtsp_dsm_save_fax_config:

   Fax Relay=ENABLED

   Primary Fax Protocol=T38_FAX_RELAY, Fallback Fax Protocol=NONE_FAX_RELAY

   Fax Relay CM Suppression :=ENABLED, Fax Relay ANS Suppression :=DISABLED

   Fax Parameters Set By=MGCP Call Type

Can some one kindly suggest how to make it work on H323, also how we can force disabling cisco fax relay?

12 REPLIES

Fax is not working on H323

Try this:

voice service pots

fax rate disable

HTH

--
Jorge Armijo

Please remember to rate helpful responses and identify helpful or correct answers.

-- Jorge Armijo Please remember to rate helpful responses and identify helpful or correct answers.

Fax is not working on H323

Hi Jorge,

Thanks for your advise. It works as I hear fax tones.

But still in the logs I see primaty fax protocol as Cisco Fax Relay. Why its showing like this? Is this the default behaviour?

Thanks.

Fax is not working on H323

That's becuase the IOS will always try to use Cisco Fax Relay as the first fax protocol, to avoid that, you need to configure under voice service voip:

voice service voip

fax protocol none

After adding that command, you have to re configure whatever fax protocol you want to use.

HTH

--
Jorge Armijo

Please remember to rate helpful responses and identify helpful or correct answers.

-- Jorge Armijo Please remember to rate helpful responses and identify helpful or correct answers.

Fax is not working on H323

Incoming now works with both MGCP and H323. Now I have the problem with Outgoing fax. When the port is configured as MGCP, either I need to remove allow-connections h323 to h323 or modem passthrough nse codec g711ulaw command to make that work. I am bit confused on this. Could you help?

Fax is not working on H323

Well, that's weird...

Can you post a debug for a failing fax call?

deb mgcp pack

deb ccm-manager back pack

deb voice ccapi inout

deb isdn q931

Also, please post the complete full configuration.

--
Jorge Armijo

Please remember to rate helpful responses and identify helpful or correct answers.

-- Jorge Armijo Please remember to rate helpful responses and identify helpful or correct answers.

Re: Fax is not working on H323

Hi,

Please find the attached debugs, for failed call and working call when I made change in configs.

It was captured during nonbusiness hours. So you will find call for only fax.

Thanks

Fax is not working on H323

I don't quite understand the problem, are you using MGCP or H323?

What's the need of having mixed protocols?

Unless you're testing MGCP Fallback, it should work with with MGCP or H323 separately.

--
Jorge Armijo

Please remember to rate helpful responses and identify helpful or correct answers.

-- Jorge Armijo Please remember to rate helpful responses and identify helpful or correct answers.

Fax is not working on H323

As I mentioned earlier, we are using MGCP for that particular fax port and the gateway we use as H323.

Even I'm not pretty sure about using mixed protocol, I believe this gateway gonna used to support call center calls. SInce MGCP is easy for configs they might have confiugred only the port as MGCP endpoint.

Now its not working with both the cases, not in mgcp as well as fallback mode. Can you reveiw the debugs and see why I have to remove "modem passthrough" command from voice service voip section which of our standard config and works well with all other gateway of ours. Please help here.

Fax is not working on H323

Hi Jorge,

Can you help?

Thanks.

Fax is not working on H323

Got it. Interesting, can you please post the latest complete config so I can review it along with the debugs?

--
Jorge Armijo

Please remember to rate helpful responses and identify helpful or correct answers.

-- Jorge Armijo Please remember to rate helpful responses and identify helpful or correct answers.

Re: Fax is not working on H323

Please find the attached file having both configs and debugs which you requested.

Fax is not working on H323

hi Jorge,

Hope you are looking on this. Did you get the issue?

Thanks

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